Timothy Keller addresses the proposition that evil’s presence in the world disproves the existence of a God:
Philosopher J. L. Mackie makes this case against God in his book The Miracle of Theism (Oxford, 1982). He states it this way: If a good and powerful God exists, he would not allow pointless evil, but because there is much unjustifiable, pointless evil in the world, the traditional good and powerful God could not exist. Some other god or no god may exist, but not the traditional God. Many other philosophers have identified a major flaw in this reasoning. Tucked away within the assertion that the world is filled with pointless evil is a hidden premise, namely, that if evil appears pointless to me, then it must be pointless.
This reasoning is, of course, fallacious. Just because you can’t see or imagine a good reason why God might allow something to happen doesn’t mean there can’t be one. Again we see lurking within supposedly hard-nosed skepticism an enormous faith in one’s own cognitive faculties. If our minds can’t plumb the depths of the universe for good answers to suffering, well, then, there can’t be any! This is blind faith of a high order.
The fallacy at the heart of this argument has been illustrated by the “no-see-ums” illustration of Alvin Plantinga. If you look into your pup tent for a St. Bernard, and you don’t see one, it is reasonable to assume that there is no St. Bernard in your tent. But if you look into your pup tent for a “no-see-um” (an extremely small insect with a bite out of all proportion to its size) and you don’t see any, it is not reasonable to assume they aren’t there. Because, after all, no one can see ’em. Many assume that if there were good reasons for the existence of evil, they would be accessible to our minds, more like St. Bernards than like no-see-ums, but why should that be the case?” (The Reason for God, Chapter 2)